Fuse



Patented Oct. 16, 1945 UNITED STATES PATENT OFFICE FUSE Application April 30, 1943, Serial No. 485,099

(Cl. D-127) 10 Claims.

This invention relates to electric fuses of the expulsion type and has to do, in part, with improvements in fuse-links and, in part, with a 4novel fuse cartridge and fuse-link combination.

Two distinct objects are achieved. One of these is the effectuation, in a very simple way, of a closure for the discharge endl of the fuse cartridge whereby to exclude insects which sometimes import mud and other substances in such quantities as to impede operation of the fuse; and the other object is to devise a fuse-link which requires no anchorage outside the fuse cartridge and which, therefore, is particularly well adapted for use in bayonet type fuses.

In the preferred construction herein described, the fuse-link comprises a fusible section and a retracting spring which functions to separate the terminals of the fusible section when a blowout occurs. The fuse-link is designed to be inserted in the cartridge at the discharge end of the latter and it has a conically shaped terminal which makes good electrical contact with the ferrule attached to the lower end of the cartridge and serves as a closure member to exclude insects etc. from the cartridge bore without interfering with normal operation of the fuse. At the same time the conically shaped contact terminal constitutes an anchorage member for the lower end of the Afuselink.

A conventional fuse-link such as commonly employed in expulsion fuses includes, as one terminal, a iiexible conductive leader which is utilized to pull the fuselink into the cartridge and is then fastened, usually under tension, to a binding post exterior of the cartridge. But that kind of fuse-link cannot conveniently be adapted for use in bayonet type fuses unless modified in a way wihch renders it somewhat complicated to install. Therefore, in order to facilitate installation of the link while eliminating the usual flexible leader, the subject fuselink, in its preferred form, is provided with a telescopically extensible or equivalent terminal member which, when extended, renders the over-all length ofthe unstretched fuse-link sufficient to reach all the way through and beyond the cartridge bore so that the extruded end can readily be grasped by the installerwhereupon the fuse-link is stretched by the installer to tension the retracting spring, and the upper terminal of the link is anchored in a manner effective to retain the link under tension While securing it in place in the cartridge.

My new fuse-link is characterized by simplicity of construction, economy of manufacture, and ease of installation and replacement.

In the drawing which accompanies this specication:

Fig. 1 is a vertical sectional view of a fuse cartridge with a fuse-link in course of installation;

Fig. 2 shows the same assemblage as Fig. 1 after the fuse-link installation has been completed; and

Fig. 3 depicts a modification.

ri'he fuse cartridge, which includes tube l together with upper ferrule 2 and lower ferrule 3, is a component part of an entire expulsion fuse structure of the bayonet type shown in the copending application of Chester W.' Brown, Serial No. 466,512, filed November 2l, 1942, but obviously may be adapted by slight modification for use in other styles of expulsion fuses employing functionally similar cartridges. Therefore, I do not wish it to be supposed that the utility of my invention is limited to bayonet type fuses.

Tube l may be of horn ber, but usually is composed of Bakelite lined with horn fiber, which latter has the capacity to emit arc-extinguishing gas or vapor when heated by the arc which strikes when the fuse-link blows in response to a heavy over-load or short circuit.

Contact and retainer member 4 and the balls 5 together with attaching screws 6 constitute portions of the locking mechanism which characterizes the bayonet fuse of the aforementioned Brown application wherein they are fully described. Those parts bear no indispensable relation to the present invention and for that reason they will not be further described herein.

The upper end of ferrule 2 is threaded externally at 2a to engage a complemental internal thread. in a cap member, not shown, which forms a part of the fuse housing.

Electrical connection is effected with the upupper end of the cartridge and enclosed fuselink by way of contact springs 4, and with the lower end of the cartridge and fuse-link via ferrule 3.

The vfuse-link extending through the bore of I2 and strain wire I3 attached at their upper ends to a stud I4 which is detachably threaded into a coupling member I5. The lower ends of the fuse and strain wires are attached to lower terminal II-which latter comprises a frustreconical lower terminus IIa and a central stem IIb. A metal sleeve I6 attached to stud I4 serves as a securing medium for a fiber tube I1 which depends `therefrom and encases the fuse and strain wires. The lower end of tube I'I is unattached. It will be evident that upon blowing of the fuse, stud I4 together with tube I1 becomes free to move upwardly under the impetus of spring 8, while terminal II `becomes free to drop out or to -be blown out by the pressure generated within the cartridge.

The lower end of retracting spring 8 is attached to coupling member I while its upper end is attached to upper terminal member 1. Said spring is under tension when the 'fuse-link is in place, asper Fig. 2, and is thus operative quickly to Y elevate parts I4, I5, Io, and l'I when the fuse blows.

In order to avoid a heavy current flow through the retracting spring, there is provided in shunt thereto the flexible conductor 9. The latter is so flexible that it readily collapses as the spring contracts.

Obviously, the fuse-link must be inserted in the cartridge from the lower end thereof; and it is not convenient to use a ilexible leader as the upper terminal of the fuse-link because of diculties involved in effecting an anchorage and at the same time keeping the upper end of the cartridge sealed, while avoiding complexity and ensuringagainst the consequences of negligence on the part of linemen in making fuse-link re'- placements. So, for the purpose of avoiding the use of a exible leader as the upper terminal, while at the same time making it easy to effect a replacement installation wherein the upper terminal connection will not become dislodged, even though the lineman may be careless about the quality of his workmanship, I have devised the upper fuse-link terminal I and complementary cartridge constructionwhich will now be described and explained.

vIt should first be pointed out that when the fuse-link is free the retracting spring 8 is contracted lengthwise and devoid of tension, wherefore, in the absence of special provision to the contrary, the unstretched fuse-link would be shorter than the cartridge, and it would for that reason be quite diicult to tension the spring and effect an installation of the link. In the conventional fuse-link the flexible leader meets that problem by being long enough to reach through the cartridge bore-being, vin most cases, cut to length after installation. The design of terminal I meets that problem without entailing a cutting olf operation and thus preserves the terminal for re-use in conjunction with a replacement fusible section following a blowout.

Upper terminal l comprises an elongate tubular member I8 having an external radially projecting flange Iga at its upper end and is threaded at its lower end for attachment to retracting spring 8.

The upper end of tubular member I8 is'threaded internally to receive aplug I9 which is bored coaxially with member I8 to provide a sliding iit for a rod 2 having a lower head 2I disposed within the bore of member I8 and slidable axially therein. The upperl end of rod 2B is provided ,with a head 22 designed to serve as a knob. It will be clear that rod 20 and member I8 are telescopically interconnectedthat fact being selfevident from a comparison of Figs. l and 2. Also, it will be apparent that plug I9 operates as a stop to limit the outward movement of rod 2D by enga-ging lower head 2l.

Flange I8a is designed to rest on a shoulder 2b (see Fig. 2) formed internally of ferrule 2. Thus, shoulder 2h constitutes an abutment co-operating with ferrule 3, which latter functions as a complementary abutment to resist the tension of spring 8. Y Flange Ia has an external diameter less than that of the cartridge bore and, therefore, it will readily pass through the cartridge. But, the flange width, radially, is suciently generous to effect a good and secure seat upon shoulder 2bthe inter-contact subtending a large arcuate portion of the shoulder.

A thumbscrew 22 ensures against unintended dislodgment of flange 18a from shoulder 2b, but I have found that it is practically impossiblefor said ange to become dislodged, except by intention, irrespective of thumbscrew 22'. In other words, thumbscrew 22' is largely superuous, but

it serves to make doubly sure that the fuse-link.

will remain Vin place indefinitely, provided there is no blowout.

Installation of the fuse-link is accomplished by inverting both the cartridge and fuse-link end for end and inserting the fuse-link. By so doing,

rod 2i) is caused by gravity to slide outwardly of tube I8 to its most extended position-which renders the unstretched fuse-link longer than the cartridge and enables the service man to grasp knob 22. The fuse-link is thereupon stretched by pulling on knob 22, to approximately the extent exhibited in Fig. 1 or, at least, until flange I8a can be seated on shoulder 2b--as depicted in Fig. 2. Thereafter thumbscrew 22 is turned to engage the side of member I8. But, if the serviceman neglects to adjust thumbscrew 22', no harm is likely to result.

Rod 2) may appropriately be described as a fishing rod since its sole function is to enable the service man to fish the upper terminal out of the cartridge bore suiciently to enable it to be anchored. l

When the loaded cartridge is turned right side up, rod 26 dropsV down into the bore of member I8 as illustrated in Fig. 2.

It will be observed that the lower end of the cartridge is closed against the entry of insects. The upper end likewise is closed when the cartridge is in place.

In Fig. 3 there is illustrated a modification of the upper end construction where, instead of a telescoped fishing rod, there is substituted a detachable rod 23.- Here the upper fuse-link terminal member corresponding to member I8 of Figs. l and 2 is identified by reference numeral 2t and has a flange 24a corresponding to flange Ia of Figs.rl and 2. rIhe lower end of rod 23 is screwed into Vmember 24 for the purpose of adding length to the fuse-link, and after the fuselink has been installed rod 23 is unscrewed and removed. Obviously the construction of Fig. 3 performs the same function as that of Figs. 1 and 2, but it has the disadvantage that rod 23 is not a permanent part of the fuse-link.

What is claimed is: Y

- l.l A fuse link assembly comprising: a pair of spaced terminals, a fusible section and a tension spring in series interconnecting said terminals, said spring being yieldable to permit elongation of the fuse-link and effective, when tensioned, to bias said fusible section, the terminal connected with said spring including a tubular member having a contact engaging portion and a rod telescoped with said tubular member, said rod being freely and independently movable telescopically relatively to said tubular member and oolinearly with the fuse-link, and stop means for preventing disengagement of said rod from said tubular member.

2. A fuse-link assembly comprising: a pair of spaced terminals, a fusible section interconnecting said terminals, one of said terminals being extensible and contractible co-linearly with the fuse-link and including a tubular member having a contact engaging portion and a rod telescopically engaged with and freely movable relative to said tubular member.

3. A fuse-link assembly comprising: a pair of spaced terminals, a fusible section interconnecting said terminals, one of said terminals being extensible and contractible co-linearly with the fuse-link and including a tubular member having a radially extending external protuberance operative as an anchoring means for one end of the fuse-link, and a rod telescopically engaged with and freely movable relative to said tubular member.

4. A fuse-link assembly comprising: a pair of spaced terminals, a fusible section interconnecting said terminals, one of said terminals being extensible and contractible co-linearly with the fuse-link and including a tubular member having an external flange operative as an anchoring means for one end of the fuse-link, and a rod telescopically engaged with and freely movable relative to said tubular member.

5. In combination: a fuse cartridge having a bore extending lengthwise therethrough, said cartridge having an internal shoulder near one end, and a fuse-link in said cartridge, said fuselink comprising a pair of terminals anchored to opposite ends of said cartridge, and a fusible section interconnecting said terminals, one of said terminals having an external protuberance eifecting an anchoring engagemet with said shoulder, and a fishing rod telescopically connected with and freely movable relative to said last-mentioned terminal, the over-all length of the fuse-link being extensible by moving said rod outwardly of said last-mentioned terminal.

6. In combination: a tubular fuse cartridge and a fuse-link therein, said fuse-link comprising a pair of spaced terminals, a fusible section and a tension spring in series interconnecting said terminals, said fuse-link being extensible lengthwise by stressing said spring, one of said terminals including a pair of overlapping members which are freely and independently relatively movable lengthwise of the fuse-link whereby the length of said terminal can be temporarily extended to facilitate installing the fuse-link in the cartridge, the over-all length of the fuse-link with said spring unstretched and said extensible terminal unextended being less than that of said cartridge, the over-all length of the unstretched fuse-link with said extensible terminal fully extended being greater than that of said cartridge.

7. In combination: a tubular fuse cartridge and a fuse-link therein, said fuse-link comprising a pair of spaced terminals, a fusible section and a tension spring in series interconnecting said terminals, said fuse-link being extensible lengthwise by stressing said spring, the terminal connected with said spring including a tube having a tension spring contact engaging portion and rod telescopically and freely movable independently and lengthwise of said tube whereby the length of said terminal can be temporarily extended to facilitate installing the fuse-link in the cartridge, the overall length of the fuse-link with said spring unstretched and said extensible terminal unextended being less than that of said cartridge, the over-all length of the unstretched fuse-link with said extensible terminal fully extended being greater than that of said cartridge.

S. In combination: a tubular fuse cartridge and a fuse-link therein, said fuse-link comprising a pair of spaced terminals, a fusible section and a in series interconnecting said terminals, said fuse-link being extensible lengthwise by stressing said spring, one of said terminals including a tube having a terminal engaging portion and rod telescopically movable lengthwise or' and relative to said tube whereby the length of said terminal can be temporarily extended to facilitate installing the fuse-link in the cartridge, the other of said terminals being conically shaped and operative as a closure for the discharge end of said cartridge, the over-all length of the fuse-link with all length of the unstretched fuse-link with said extensible terminal fully extended being greater than that of said cartridge.

e. In combination: a tubular fuse cartridge having conductive abutment means at each end, one or said abutment; means being a shoulder within the bore of the cartridge, and a fuse-link within said cartridge and tensioned between said abutment means, said fuse-link comprising a pair of spaced terminals engaging said abutment means individually, a fusible section and a tension spring in series interconnecting said terminals, said fuse-link being extensible lengthwise by stressing said spring, one of said terminals including a tube and rod telescoped together and relatively movable lengthwise of the fuse-link whereby the length of said terminal can be temporarily extended to facilitate installing the fuselink in the cartridge, said tube having an eX- ternal radial protuberance seated on said shoulder and serving to anchor said tube thereto, the other of said terminals being operative as a closure for the discharge end of said cartridge, the ever-all length of the fuse-link with said spring unstretched and said extensible terminal unextended being less than that of said cartridge, the over-all length of the unstretched fuse-link with said extensible terminal fully extended being greater than that of said cartridge.

10. In combination: a tubular fuse cartridge and a fuse-link therein, said fuse-link comprising a pair of spaced terminals, a fusible section and a tension spring in series interconnecting said terminals, said fuse-link being extensible lengthwise by stressing said spring, one of said terminals comprising a sleeve, a rod freely slidable in said sleeve and means within said sleeve preventing complete disengagement of said rod from said sleeve, said sleeve and rod being operative to extend the length of said fuse-link whereby the insertion of said fuse-link in said fuse cartridge is facilitated, said rod being nested in said sleeve when said fuse-link is mounted in said cartridge.

VILLIAM O. SCHULTZ. 

